Key takeaways
- QUIKRETE suggests starting with about 6 pints of water for an 80 lb bag, up to about 9 pints.
- Aim for a stiff, moldable mix with no dry pockets or standing puddles.
- Keep curing for 5 days at 70°F or warmer, or 7 days from 50°F to 70°F.
For an 80 lb bag of QUIKRETE Concrete Mix, start with about 6 pints of water and expect to use no more than about 9. These figures are for that product, so follow the directions on your bag if you use another.
| Bag size | Starting water | Maximum expected water |
|---|---|---|
| 40 lb | 3 pints | 4½ pints |
| 50 lb | 3½ pints | 5½ pints |
| 60 lb | 4 pints | 7 pints |
| 80 lb | 6 pints | 9 pints |
| 90 lb | 7 pints | 10 pints |
How to mix
By hand: empty the bag into a mixing container and add the starting water. Work it with a shovel, rake or hoe, adding water as needed, until the mix is stiff and moldable with no dry pockets. Don't leave standing puddles.
With a mixer: add the water, start the mixer, then add the concrete. QUIKRETE says to allow at least 1 cubic foot of mixer capacity for each 80 lb bag mixed at one time.
Pouring a slab: QUIKRETE's steps
- Dampen the sub-grade, without leaving puddles.
- Fill the form to full depth, working from one end to the other.
- Strike off and float right away.
- Run an edging tool or trowel along the forms.
- Cut control joints 1 inch deep, every 6 to 8 feet.
- Wait until the water has evaporated from the surface before troweling or broom finishing.
Work out your quantities first with the concrete slab calculator, and check how thick your slab should be.
How long to cure
QUIKRETE calls curing one of the most important steps, because it increases strength and durability. It says to start as soon as possible and continue for:
| Weather | Keep curing for |
|---|---|
| 70°F or warmer | 5 days |
| 50°F to 70°F | 7 days |
Its options include a cure-and-seal product, covering the surface with wet burlap, plastic sheeting or waterproof paper, or keeping it wet with a lawn sprinkler. Near freezing, curing slows considerably. Hot, dry or windy weather can cause finishing problems and shrinkage cracks.
How strength builds
QUIKRETE lists these typical results for its Concrete Mix:
| Age | Compressive strength |
|---|---|
| 7 days | 2,500 psi |
| 28 days | 4,000 psi |
How much water to have on site
At QUIKRETE's figures for 80 lb bags, plan your water supply before you start:
| 80 lb bags | Water needed |
|---|---|
| 10 | 8 to 11 gallons |
| 30 | 23 to 34 gallons |
| 60 | 45 to 68 gallons |
Water also goes into rinsing tools and the mixer, so have more on hand.
Frequently asked questions
What happens if I add too much water?
QUIKRETE's maximum expected water is about 9 pints for an 80 lb bag. Aim for the stiff, moldable mix it describes rather than a runny one, and add water gradually.
How long before I can put weight on new concrete?
QUIKRETE says to wait 24 hours before putting strain on a newly set fence post, and lists strength rising through 28 days. It doesn't give one rule for every slab, so follow your bag's directions and ask your contractor about vehicle loads.
Can I pour concrete in cold weather?
Near-freezing temperatures slow curing considerably. Check your product's temperature limits before you pour.
Sources
We use primary sources where we can: building codes, federal rules and manufacturer documents. Read our editorial standards.
- QUIKRETE: Concrete Mix data sheet, product 1101